1. Field of the Invention
The present invention relates to a band braking device and to a method of manufacturing an annular brake band to be used in an automatic transmission, or the like, for a car. The present invention further relates to a technology for improving the durability of such device and band.
2. Related Background Art
A band braking device is widely employed in an automatic transmission for a car or other industrial machines, in order to apply a brake on a transmission element or a rotary element. Usually, to form the band braking device, a frictional member is bonded onto the inner peripheral surface of an annular shaped steel plate, to form a brake band. Then, the diameter of this brake band is reduced by an actuator, to thereby fasten a transmission element or a rotary element provided inside the band to apply a brake. The brake band has an anchor bracket which is fixed to the fixed end side thereof, and an application bracket to an operational end side. Note that a double-wound band braking device is recently proposed which employs a double-wound brake band so as to reduce an operational force of the actuator or to enhance the brake controllability.
For manufacturing a brake band, an assembly worker generally sets a brake band, brackets, and the like, inside an unrepresented tool, and provisionally fastens these members by spot welding for alignment. After that, the brake band, the anchor bracket, and the like, are joined and integrated together by brazing. FIG. 20 is a longitudinal cross sectional view (of a first conventional device) for showing a joint between a brake band (the outer band of a double-wound brake band) 15 and an anchor bracket 21. In this Figure, a reference numeral 41 denotes a welded portion by the spot welding, and 35 denotes metallic wax used in the brazing, such as brass wax.
Incidentally, in the above-mentioned brake band, a large braking torque acts at braking. For this reason, when the brake band is used over a long time to exceed its predetermined durability, the metallic wax 35 is gradually peeled off from the joint, and the like, between the outer band 15 and the anchor bracket 21, and the peeled-off portion of the wax finally reaches the welded portion 41, as shown in FIG. 21. As generally known, since the welded portion 41 by the spot welding is structurally fragile, the stress is concentrated on a portion surrounding the welded portion 41. For this reason, when the thickness of the outer band 15 is set to be small in order to reduce the weight, a crack 43 is generated on the outer band 15 in the vicinity of the welded portion 41, as shown in FIG. 21, which may eventually destroy the outer band 15. In such case, the transmission function is impeded, and moreover a long period of time is required to repair the outer band 15. Thus, conventionally, it is necessary to employ a thick band as the outer band 15, which inevitably increases the weight of the band braking device, and consequently, the weight of the automatic transmission.
Meanwhile, as shown in FIG. 22, such a method is employed in some cases by which a through hole 51 is formed on the outer band 15, and a cylindrical convex portion 53 formed on the anchor bracket 21 is fitted in the through hole 51, so as to caulk the tip end of the convex portion 53 (a second conventional device). However, even by this method, the substantial width of the outer band 15 becomes small at a position where the through hole 51 is formed, so that, when the thickness of the outer band 15 is set to be small, a crack 43 may be generated on the outer band 15, as shown in FIG. 23. Another method is proposed, as shown in FIG. 24, by which the outer band 15 and the anchor bracket 21 are fixed together both by caulking and by brazing (a third conventional device) However, even by such method, the same problem occurs when the peeled-off portion of the metallic wax 35 reaches the caulking position.
The present invention has been contrived taking the above circumstances into consideration, and aims of providing a band braking device in which secured fixation between a brake band and a bracket, etc., is realized, while maintaining the strength of the brake band, as well as a method of manufacturing a brake band.
In order to solve the above problems, according to a first aspect of the present invention, there is proposed a band braking device having an annular brake band which has a frictional surface formed on the inner peripheral side thereof and a bracket fixed to an end portion thereof, characterized in that:
concave or recessed portions are formed on one of the bracket and the brake band, and convex or projected portions are formed on the other to be engaged with the concave or recessed portions.
According to this aspect of the present invention, for example, a plurality of concave or recessed portions are formed on either one of the brake band and the bracket, and the convex or projected portions are formed on the other to be fitted in these concave or recessed portions, so as to realize the alignment without forming a fragile portion in the brake band.
In the band braking device according to the first aspect of the present invention, the bracket and the brake band may preferably be fixed to each other by brazing. In this case, since there is no fragile portion in the brake band, the brake band is not destroyed even when the peeling-off of the wax progresses.
In the band braking device according to the first aspect of the present invention, the concave or recessed portions may be preferably formed on the bracket while the convex or projected portions on the brake band. In this case, even when the convex or projected portions are formed; for example, by pressing, no thin portion is formed in the brake band, so that the strength of the brake band may be maintained more securely.
In the band braking device according to the first aspect of the present invention, the concave or recessed portions and the convex or projected portions may be formed in the elongated forms extending in the circumferential direction of the brake band. Thus, even when, for example, the concave or recessed portions are formed on the brake band, the thickness of the concave or recessed portion in the width direction is less reduced so that the strength of the brake band may be maintained still more securely.
In the band braking device according to the first aspect of the present invention, the brake band may be formed as a double-wound brake band which comprises an intermediate band and an outer band. In this case, there is no fragile portion generated by the spot welding or a through hole even in an intermediate band or outer band having a small width, so that the strength thereof may be maintained still more securely.
According to the first aspect of the present invention, there is proposed also a method of manufacturing an annular brake band which has a frictional surface formed on the inner peripheral side thereof and a bracket fixed to an end portion thereof, comprising the steps of:
forming concave or recessed portions on either one of the bracket and the brake band, and convex or projected portions on the other to be engaged with the concave or recessed portions; and
bringing the concave or recessed portions into engagement with the convex or projected portions so as to bond the bracket and the brake band together by brazing.
According to a second aspect of the present invention, there is proposed a band braking device having an annular brake band which has a frictional surface formed on the inner peripheral side thereof and a bracket fixed to an end portion on the outer peripheral side thereof, wherein the bracket and the brake band are bonded together by an adhesive member.
In the case of the band braking device according to this aspect of the present invention, after, for instance, a thermosetting adhesive is applied on the bracket or the brake band, the both members are brought into contact pressure and is heated to be securely bonded together.
Also, in the band braking device according to the second aspect of the present invention, preferably at least one of the bonded surfaces of the bracket and the brake band was subjected to a primer treatment. According to this feature of the second aspect of the present invention, after, for instance, a primer is sprayed onto the bonded surfaces of the bracket and the brake band, the both members are securely bonded together by an adhesive.
Also, in the band braking device according to the second aspect of the present invention, the bracket and the brake band may be preferably bonded together by caulking. According to this feature of the second aspect of the present invention, after, for instance, convex or projected portions formed on the bracket are fitted in holes formed on the brake band, the tip ends of the convex or projected portions are enlarged so that the both members are brought into contact by caulking, whereby the both members are bonded together by adhesive.
Also, in the band braking device according to the second aspect of the present invention, the bracket and the brake band may be preferably fixed to each other by spot welding. According to this feature of the present invention, after, for instance, the bracket is aligned with the brake band and the both members are fixed to each other by spot welding, the both members are bonded together by adhesive.
Also, in the band braking device according to the second aspect of the present invention, the concave or recessed portions are preferably formed on either one of the bracket and the brake band while the convex or projected portions are formed on the other to be engaged with the concave or recessed portions. In this case, after, for instance, the convex or projected portions formed on the bracket are fitted in the holes formed on the brake band, the both members are securely bonded together by an adhesive.
Also, according to the second aspect of the present invention, there is proposed a method of manufacturing an annular brake band which has a frictional member formed on the inner peripheral side thereof and a bracket fixed to an end portion on the outer peripheral side thereof, comprising the step of: thermally bonding the frictional member and the bracket at the same time to the brake band, after interposing a thermosetting adhesive between the frictional member and the bracket. In this method according to the second aspect of the present invention, after, for instance, the thermosetting adhesive is applied on the bonded surfaces of the frictional member and the bracket, these members are aligned with respect to the brake band and fixed by means of a jig, to be heated for a predetermined time inside a furnace, or the like.